The invention relates to information communications architecture designed more particularly to be installed in an industrial process control system so as to enable digitized information to be transmitted in time shared manner between programmed operating units of the system.
As is known, managing an industrial process control system involves the presence of communications architecture in order to transmit information between the various programmed operating units that can act in the control of the process, so that the information is transmitted in a manner well suited to the various needs encountered. Such an architecture is commonly made up of one or more xe2x80x9cindustrialxe2x80x9d local area networks organized around one or more bus-type links.
It is conventional in such systems to use the links in time shared manner for transmitting information between the programmed operating units. It is common in the field of industrial process control to have very strict transmission constraints for certain information. That involves implementing xe2x80x9cdeterministicxe2x80x9d local area networks which are organized to make it possible to comply with the time constraints for transmitting information for which such constraints are necessary, i.e. which convey information within a determined time limit, or which aim to achieve such a result.
It is then known to enable information whose transmission is subject only to relatively flexible constraints in terms of urgency to make use of the lapses of time that are left available on a more or less regular basis by the priority information which is subject to constraints that are more severe.
In many operating cases, it is advantageous to be able to access, at will and without there necessarily being any urgency, information contained in a memory of any one of the programmed operating units of a system, e.g. by means of another programmed unit or of a computer, via the communications architecture of the system, and regardless of the location of said other unit or of said computer relative to the system.
In particular, when the operation of a system involves a wide variety of equipment involving various users taking action that is not necessarily plannable, it is advantageous for those users to be able to access easily the information that they need, via the communications architecture of the system, and optionally from the outside, whenever such information is stored accessibly by a programmed operating unit of the system.
Such access must preferably be possible for users who can differ widely. One known system thus makes provision to use a communications architecture that uses an information access technique that is implemented more particularly in the context of the Internet.
For that purpose, the information that is available in the programmed operating units and in particular the information that has been collected via the communications architecture of the system, is inserted into HTML pages installed in a programmed operating unit of the system that is constituted by a dedicated computer in which an HTTP server is installed. That computer is, for example, connected to an external network 0 which uses the Internet techniques, or even to the Internet itself. Any user who has access to a suitably-equipped computer assumed, in that example, to be connected to the network 0, or who has access to a functionally-equivalent programmed unit of the system, can then become acquainted with the information contained in the HTML pages, stored in the dedicated computer.
However, that solution is not entirely satisfactory in particular as regards how up-to-date the stored information is. Unfortunately, that can be crucial in a system in which certain items of equipment and in particular certain site units are used in real time and must not be disturbed during the control of the process.
The invention therefore provides a time-shared communications architecture for communicating digitized information for an industrial process control system, which architecture is organized around at least one industrial local area network conveying deterministic traffic between various programmed operating units, which units process and store information which can be accessed by at least one other programmed operating unit via said architecture.
According to a characteristic of the invention, said architecture includes various programmed operating units in particular comprising units situated at an intermediate level or at a process interface level or at a site monitoring/control device level, which units individually include servers of the HTTP type so as to be capable of sending optionally interactive computer documents in response to requests received from another unit of the system or from a computer, in particular external to the system, equipped with an HTTP/TCP/IP protocol stack and acting as a customer, in the context of messaging traffic making use of the transmission possibilities constituted by the time slots left available by the deterministic traffic of the industrial local area network(s) of the system, without disturbing the priority and deterministic interchange related to the real time control of the process.
According to another characteristic of the invention the architecture is constituted in a manner such that units are organized in one or more clusters around at least one industrial local area network of the site bus type which is specific to a cluster and which connects the units of the cluster to at least one shared unit, optionally serving as a gateway or as a router to another industrial local area network serving at least one other programmed unit of a higher level of the architecture, in particular a supervision unit and/or optionally a unit serving as a gateway or router to an external communications network, so that the HTTP server of a cluster unit equipped with such a server responds with an optionally interactive computer document if a request is addressed to it, via at least one of the networks, by another unit or by a computer, in particular external to the system, equipped with an HTTP/TCP/IP protocol stack, when the request concerns inserting or extracting parameters and/or variables stored at the unit that includes said server.